content: /*
   * Copyright (C) 2012 CyberAgent
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   * http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package com.mitakeran.magicfilter.filter.base.gpuimage;
  
  import android.opengl.GLES20;
  
  /**
   * saturation: The degree of saturation or desaturation to apply to the image (0.0 - 2.0, with 1.0 as the default)
   */
  public class GPUImageSaturationFilter extends GPUImageFilter {
      public static final String SATURATION_FRAGMENT_SHADER = "" +
              " varying highp vec2 textureCoordinate;\n" +
              " \n" +
              " uniform sampler2D inputImageTexture;\n" +
              " uniform lowp float saturation;\n" +
              " \n" +
              " // Values from \"Graphics Shaders: Theory and Practice\" by Bailey and Cunningham\n" +
              " const mediump vec3 luminanceWeighting = vec3(0.2125, 0.7154, 0.0721);\n" +
              " \n" +
              " void main()\n" +
              " {\n" +
              "    lowp vec4 textureColor = texture2D(inputImageTexture, textureCoordinate);\n" +
              "    lowp float luminance = dot(textureColor.rgb, luminanceWeighting);\n" +
              "    lowp vec3 greyScaleColor = vec3(luminance);\n" +
              "    \n" +
              "    gl_FragColor = vec4(mix(greyScaleColor, textureColor.rgb, saturation), textureColor.w);\n" +
              "     \n" +
              " }";
  
      private int mSaturationLocation;
      private float mSaturation;
  
      public GPUImageSaturationFilter() {
          this(1.0f);
      }
  
      public GPUImageSaturationFilter(final float saturation) {
          super(NO_FILTER_VERTEX_SHADER, SATURATION_FRAGMENT_SHADER);
          mSaturation = saturation;
      }
  
      @Override
      public void onInit() {
          super.onInit();
          mSaturationLocation = GLES20.glGetUniformLocation(getProgram(), "saturation");
      }
  
      @Override
      public void onInitialized() {
          super.onInitialized();
          setSaturation(mSaturation);
      }
  
      public void setSaturation(final float saturation) {
          mSaturation = saturation;
          setFloat(mSaturationLocation, mSaturation);
      }
  }
  